Synthesis of vitamin bs



- amino- 4 -alkoxymethyl- 5 Stanton a.

of New .17 ersey No Drawing.

Han-ls, estfield, n. Merck & Ca, fine, Railway, N.

3., asslg nor to a corporation Urigir'zall. application October 28, 1939, Serial N 301,733.

Divided and this application December 20, 1941, Serial No 423,771

15 Clas.

This invention relates to the synthesis of vitamin Be and to various intermediates employed in its production, and is a division of my co-pending application, Serial No. 301,733, filed October 28, 1939.

Ina co-pending application, Serial No. 267,603, is shown a process for the production of vitamin Be, in which 3-cyano-4-ethoxymethyl-5-nitro-6- methyl-pyridone-2 is chlorinated with phosphorus pentachloride, reduced with hydrogen in the presence of a catalyst, diazotized, and the resulting product hydrolyzed to form vitamin Be.

I have discovered that vitamin B8 may be obtained by reducing 3-cyano-4-alkoxymethyl-5- nitro-B-methyl-pyridone-Z to form 3-cyano-4 alkoxymethyl- 5 -amino 6 methyl-pyridone-2, treating the latter compound with phosphorus pentachloride and phosphoru oxychlorlde to form 2-methyl 3 amino 4 alkoxymethyl 5 cyano-G-chloropyridine,reducing the latter compound with hydrogen in the presence of a catalyst to form 2-methyl-3-amino-4-alkoxymethyl- 5-aminomethylpyridine, hydrolyzlng the latter compound to form 2-methyl-3-amino-4-hydroxymethyl-5-aminomethylpyridine, which on diazotization yields vitamin B8.

Variations may be made in this synthesis. For example, 2-methyl- 3 -amino-4-alkoxymethyl-5- cyano-S-chloropyridina may be acetylated with acetic anhydride to form 2-methyl-3-diacetyl- -cyano- 6 -chlorpyridine, hydroeenat ng the latter compound to form Z-methyl- 3 -diacetylamino- 4 -alkoxymethyl-- aminomethylpyridine, hydrolyzing the latter compound to form 2-methyl-3-amino-4-alkoxymethyl-5-aminomethylpyridine, hydrolyzing the latter compound to form 2-methyl-3-amino-4- hydroxymethyl-5-aminomethylpyridine, and diazotlzing the latter compound to form vitamin B6.

Alternatively, 2-methyl- 3 -amino- 4 -alkoxymethyl-5-cyano-G-chloropyridine may be treated with acetic anhydride under somewhat less drastic conditions to form 2-methyl-3-acetylamino-4 alkoxymethyl- 5 -cyano- 6 -chloropyridine, which may be used in the production of vitamin B6 according to the same procedure as outlined above for the corresponding diacetylamino derivative.

I have also discovered that 3-cyano-4-alkoxymethyl- 5 -amino- 6 -methyl pyridone-2 may be treated with acetic anhydride to form 3-cyano-4- alkoxymethyl- 5 -acetylamino- 6 methyl-pyridone-2. This compound is also obtained when 3-cyano- 4 -alkoxymethyl 5 nitro 6 methylpyridone-2 is reduced catalytically in the presence of acetic anhydride. However, if 3-cyan0-4- night at room temperature (30 0.).

alkoxymethyl- 5 -'amino- 6 -methyl pyridone=2 is heated with acetic anhydride, .i-cyano-i-alkoxymethyl-5-diacetylamino-B-methyl-pyridone --2. is

formed.

wherein R is an alkyl radical, R is a member of I the group amino, acetylamino and diacetylamino, R is a member of the group cyano and aminomethyl, and R3 is a member of the group chlorine and hydrogen.

The following examples illustrate method of carrying out the present invention, -but it is to be understood that these examples are given by way of illustration and not 01' limitation. Example 1 A mixture of 14.8 gm. of 3-cyano-4-ethoxymethyl-5-nitro-6-methyl-pyridone-2, 900 cc. of alcohol, and 0.5 gm. of Adams catalyst is hydrogenated under three atmospheres pressure. The hydrogenation is completed in approximately 1 hour, when three mols of hydrogen are taken up. The mixture is filtered and the filtrate evaporated to dryness. The 3-cyano-4-ethoxymethyl- S-amino-6-methyl-pyridone-2 obtained i purified by recrystallization from alcohol. Yield 8.3 gm., M. P. 250-255 C. Additional material may be obtained from the mother liquor.

If desired, 4-alkoxymethyl-pyridones, other than i-ethoxymethyl-pyridone, may be used as a starting material, such as 4-methoxymethyl, etc.

2 gm. of 3-cyano-4-ethoxymethyl-5-amino-6- methyl-pyridone-2 are treated with 15 to 20 cc. of phosphorus oxychloride'and 4 gm. of phosphorus pentachloride, and allowed to stand over- The phosphorus oxychloride is removed under reduced pressure, and the residue treated with ice water. On neutralization with ammonia, crystalline 2- methyl 3 amino 4 ethoxymethyl-5-cyano-6- chloropyridine separates out. Yield, 0.38 gm. 16.5%). After three recrystallizatlons from alcohol, it melts at l46-147 C.

A solution of 3.8 gm. of 2,-methyl-3-amino-4- 'ethoxymethyl-5-cyano-fi-chloropyridine in 20-25 cc. of acetic anhydride is refluxed for one-half hour. The acetic anhydride is removed by distillation under reduced pressure and the last trace destroyed by distilling with alcohol. methyl 3 diacetylamino-4-ethoxymethyl-S-cyano6-chloropyridine crystallizes out of the alcohol, and is purified by recrystallization from 95% alcohol. Yield, 4.3 gm. or 82.5%; melting point 90-92 C. This compound is readily hydrolyzed by acid medium to the moncacetyl compound.

A mixture of 3.09 gm. of 2-methyl-3-diacetylamino 4 ethoxymethyl-5-cyano-6 chloropyridine, 100 cc. of glacial acetic acid, 0.82 gm. (one equivalent) of sodium acetate, 10 gm. of 5% palladium charcoal and 0.5 gm. of Adams catalyst are hydrogenated under three atmospheres pressure. After the theoretical amount of hydrogen is absorbed, the solution is filtered, concentrated to a syrup, taken up in alcohol, and filtered from the separated sodium chloride. A solution of 2.5 gm. of picric acid in 10 cc. of alcohol is added to the solution of Z-methyl-B-diacetylamino-4-ethoxymethyl-S-amino-methylpyridine, and after several minutes of scratching, crystallization starts. The picrate of 2-methyl-3- diacetylamino-4ethoxymethyl-5-amino-methylpyridine obtained is purified by recrystallization from alcohol. Yield 2.6 gm.; M. P. 190l9l C.

7.7 gm. of the picrate of 2-methyl-3-diacetylamino-4-ethoxymethyl-5-aminomethylpyridine is dissolved in 25 cc. of hydrochloric acid (1: 1), and the picric acid is extracted with 20 cc. of nitrobenzene and then with ether until no yellow color remains. The mixture is refluxed for one and one-half hours. then evaporated, and. the residue recrystallized from a mixture of alcohol and acetone. The 2-methyl-3-amino-4-ethoxymethyl-5-aminomethylpyridine-dihydlrochloride, when dried at 100 C. under a high vacuum, melts at 204 to 205 C. I! desired, the free base of this compound may be obtained by treatment with an alkali, evaporation to dryness, and extraction with an organic solvent, such as alcohol or acetone.

2.24 gm. of 2-methyl-3-amino-4-ethoxymethyl-5-aminomethylpyridine dihydrochloride' are dissolved in 34 cc. of 2.5 N hydrochloric acid, and heated in a bomb tube- The slightly colored solution is filtered with charcoal, and concentrated to dryness under reduced pressure. The dihydrochloride of arnino-4-hydroxy methyl-5-amino-methylpyri dine obtained is recrystallized from water and alcohol. Yield 1.44 gm, (76.7%), M. P. 235-237? C. The free base of this compound may be obtained by treatment with an alkali, evaporation to dryness, and extraction with an organic solvent, such as alcohol or acetone.

A solution of 1.28 gm. of 2-methyl-3-amino-4 hydroxymethyl-5-aminomethylpyridine-dihydrochloride in 22 cc. of'water and a solution of 2.2 gm. of sodium nitrite are added simultaneously to 45 cc. of hot (90-95 C.) 2.5 N hydrochloric acid. The yellow solution is concentrated to dryness under reduced pressure, and the residue washed with acetone. which removes some of the color. The vitamin B hydrochloride is extracted from the sodium chloride with not absolute alcohol. This solution is filtered with charcoal, and concentrated to a small volume. On addition of acetone. the vitamin B5 hydrochloride crystallizes. Yield, 0.5 gm. (45.4%); M. P. 208 C.

Example 2 2-methyl-3- ture of cc. of anhydrous pyridine and 3.5 cc. of acetic anhydride. After ten minutes, the solution is poured into about 10 cc. of ice water, whereupon S-cyano-4-ethoxymethyl-5-diacetylamino-6-methyl-pyridone-2 separates and is filtered oil. It is purified by recrystallization from a small quantity of alcohol. M. P. 176 C.

Alternatively, 5.1 gm. of 3-cyano-4-ethoxymethyl-S-amino-6-methyl-pyridone-2 is refluxed with 25 cc. of acetic anhydride for 2 hours. The acetic anhydride is removed by concentration in vacuo, and is concentrated several times with alcohol to remove the acetic anhydride. The product is an oily material which crystallizes after standing for several days. After three recrystallizations from 95% alcohol, the 3-cyano- Yield, 1.25 gm.;

4-ethoxymethyl-5-diacetylamino-fi-methyl-pyri- 101' 4 hours at 175-180 C.

done-2 melts at 1'76" C.

Example 3 1 gm, of 3-cyano-4-ethoxymethyl-5-amino-6- methyl-pyiidone-Z is dissolved in 10 cc. of warm acetic anhydride which is then removed by even: oration under reduced pressure. The residue is treated with ethyl acetate which dissolves the unchanged starting material and leaves 3-cyano- 4 ethoxymethyl 5 monoacetylamino 6 methyl-pyridone-2 as'a residue. It is recrystallized from ethyl alcohol, M. P. 260 C.

Alternatively, 23.5 gm. of 3-cyano-4-ethoxymethyl-5-nitro-6-methyl pyridone-2 are dissolved in 200 cc. of acetic anhydride and hydrogenated in the presence of 3 gm. of Adams catalyst. After 3 mols of hydrogen are absorbed, the reduction is stopped and the material filtered. 3 cyano 4 ethoxymethyl 5 monoacetyl amino-6-methyl-pyridone-2 is recovered by recrystallizing the precipitate from 95% alcohol. Yield of first crop 13.3 gm., or 53.4%. On evaporation of the mother liquor an additional quantity of material is obtained.

Example 4 2 gm. of 2-methyl-3-amino-4-ethoxymethyl-5- cyano-fi-chloropyridine are dissolved in 10 cc. of warm acetic anhydride and allowed to crystallize by cooling. The mixture is filtered and 1 gm. 0! starting material recovered. The acetic anhydride is decomposed by mixing with cold water. The product is extracted with tour 10 cc. portions of chloroform, and the extracts washed with cold, saturated sodium bicarbonate solution until neutral, and finally with water and dried over calcium chloride. The chloroform is evaporated oil and the residue 2 methyl 3 acetylamino 4 ethoxymethy1-5-cyano-6-chloropyridine recrystallized from 95% alcohol, M. P. 134-136 C.

Modifications may be made in carr i g out the present invention without departing from the spirit and scope thereof, and I am to be limited only by the appended claims.

I claim: 1. Compounds of the formula a on me Cl wherein R is an alkyl radical, R1 is a member of the group consisting of amino, acetylamino. and diacetylamino; and salts thereof.

' 2. 2 methyl 3 amino 4 alkoxymethyl 5-cyano-6-chloropyridine.

attest? a 3. 2 methyl 3 acetylamino -'4 alkoxy methyl--cyano-6-chloropyridine.

4. 2 methyl 3 diacetylamino 4 alkoxy methyl-S-cyano-fi-chloropyridine.

5. 2 methyl 3 amino ethoxymethyl 5-cyano-6-chloropyridine.

6. 2 methyl 3 acetylamino methyl-E-cyano-G-chloropyridine.

7. 2 methyl 3 diacetylamino 4 ethoxy methyl-5-cyano-6-chloropyridine. I

8. In the synthesis of vitamin Be the step which comprises reacting 3 cyano 4-alkoxymethyl-5- amino-B-methyl pyridone-2 with phosphorous pentachloride.

9. In the synthesis of vitamin Be the step which comprises reacting 3-cyano-4-alkoxymethyI-S-actyiamiho-G-methyl pyridone-2 with phosphorous pentachloride.

10. In the synthesis of vitamin Be the step which comprises reacting 3-cyano-4-alkoxymethy1-5-diacetyiamino 6 methyl pyridone-2 with phosphorous pentachloride.

11. In the synthesis of vitamin Be the step which comprises reacting 2-methyl-3-amino- 4- alkoxymethyl 5 cyano 6 chloropyridine with acetic anhydride.

12. In the synthesis of vitamin Be, the step which comprises reacting 3-cyano-4-ethoxymethyl 5 amino -6 methyl pyridone 2 with phosphorus pentachloride.

13. In the synthesis of vitamin Be. the step which comprises reacting 2-methyl-3-amino-4- ethoxymethyl 5 cyano 8 chloropyridine with acetic anhydride.

4 ethoxy- 14. The process which comprises reacting 3-cyano 4 ethoxymethyl 5 nitro 6 methyl pyridone-2 with hydrogen in the presence of a catalyst to form 3 cyano-4-ethoxymethyl-5-amlnofi-methyl-pyridone-Z, reacting the latter compound with phosphorus pentachloride to form 2 methyl 3 amino 4 -ethoxymethyl 5 cyano-6-chloropyrldine, hydrogenating the 1atter compound in the presence of a catalyst to form- 2 methyl 3 amino 4'- ethoxymethyl S-aminomethylpyridine, hydrolyzing the latter compound to form 2-methyl-3-amino-4-hydroxymethyl-5-aminomethylpyridine. and diazotizing the latter compound to form vitamin Ba.

15; The process which comprises hydrogenating 3 cyano 4 ethoxymethyl 5 nitro 6 methyl-pyridone-2 to form 3-cyano-4-ethoxymethyl 5 amino 6 methyl pyridone 2. reacting the latter compound with phosphorus pentachloride t 0 form 2-methyl-3-amino-4- ethoxymethyl-5-cyano-6-ch1oropyridine, treating the latter compound form 2 -methyl 3 diacetylamino 4 ethoxymethyl --5 cyano 6 chloropyridine, hydrogenating' the latter compound to form 2-methyl- 3 diacetylamino 4 ethoxymethyl 5 aminomethylpyridine, treating the latter compound with hydrochloric acid to form 2-methyl-5; amino 4 ethoxymethyl 5 aminomethylpyridine, treating the latter compound with hydrochloric acid to form 2-methyl-3-amino-4-hydroxymethyl-5-aminomethylpyridine, and diazotizing the latter compound to form vitamin B6.

STANTON A. HARRIS.

with acetic anhydride to 

